Copyright 2010, John Wiley & Sons, Inc. Chapter 18 The Respiratory System.

Copyright 2010, John Wiley & Sons, Inc.

Chapter 18

The Respiratory System


Respiration: Three Major Steps1. Pulmonary ventilation

Moving air in and out of lungs

2. External respiration Gas exchange between alveoli and blood

3. Internal respiration Gas exchange between blood and cells


Organs of the Respiratory System Upper respiratory system

Nose and pharynx Lower respiratory system

Trachea, larynx, bronchi, alveoli, and lungs “Conducting zone” consists of

All airways that carry air to lungs: Nose, pharynx, trachea, larynx, bronchi, bronchioles,

and terminal bronchioles “Respiratory zone”

Sites within lungs where gas exchange occurs Respiratory bronchioles, alveolar ducts, alveolar sacs,

and alveoli


Organs of the Respiratory System


Upper Respiratory System: Nose Structure

Nostril openings – nares Septum – pperating the nostrils. Rich in blood

supply… nosebleeds (epitaxis) result from septum contusion.

Vestibule – area just inside the nostril. Covered with vibrissae (course hairs to catch microbes and chemical scents.

Nasal mucosa – this portion of the nose begins in the respiratory portion of the nasal passage. Air passes over this area carrying across the olfactory epithelium.


Sinuses – air filled cavities lines with respiratory mucosa that drains into the nose.

Cleft palate – bone separating the roof of the mouth from the base of the nose.

Cribiform plate – bone separating the roof of the nose from the base of the cranial cavitiy.


Nose

Functions Warm, humidify, filter/trap dust and microbes

Mucus and cilia of epithelial cells lining nose Detect olfactory stimuli Modify vocal sounds If obstructed, air can bypass the nose and go in

and out of the mouth.


Upper Respiratory System: Pharynx Known as the “throat” Structure

Tubelike structure about 5” in length extending from the base of the skull to esophogus.

Three regions (with tonsils in the upper two) Upper: nasopharynx; posterior to nose

Adenoids and openings of auditory (Eustachian) tubes Middle: oropharynx; posterior to mouth

Palatine and lingual tonsils are here Lower: laryngopharynx

Connects with both esophagus and larynx: food and air


Respiratory System: Head and Neck


Lower Respiratory System: Larynx “Voice box” – located between the base of the tongue and

upper end of the trachea

Made largely of cartilage Thyroid cartilage: gives triangular shape to

anterior wall. “Adam's apple”: projects more anteriorly in males Vocal cords “strung” here (lining juts inward and forms

folds) Epiglottis: leaf-shaped piece; covers airway

During swallowing, larynx moves up so epiglottis covers opening into trachea


Lower Respiratory System: Larynx


Voice Production Mucous membrane of larynx forms two pairs

of folds Upper = false vocal cords Lower = true vocal cords

Contain elastic ligaments When muscles pull elastic ligaments tight, vocal

cords vibrate sounds in upper airways Pitch adjusted by tension of true vocal cords

Lower pitch of male voice Vocal cords longer and thicker; vibrate more

slowly


Lower Respiratory System: Trachea “Windpipe” Location

Anterior to esophagus and thoracic vertebrae Extends from end of larynx to primary bronchi

Structure C-shaped rings of cartilage support trachea, keep

lumen open during exhalation Tracheostomy: opening in trachea for tube –

this is permanent


Lower Respiratory System: Bronchi, Bronchioles Structure of bronchial tree

Bronchi contain cartilage rings Primary bronchi enter the lungs medially In lungs, branching secondary bronchi

One for each lobe of lung: 3 in right, 2 in left These smaller airways

Have less cartilage, more smooth muscle. In asthma, these airways can close.

Can be bronchodilated by sympathetic nerves, epinephrine, or related medications.


Lower Respiratory System: Alveoli Alveoli: composed of three types of cells

Lined with thin alveolar cells (simple squamous); sites of gas exchange

Scattered surfactant-secreting cells. Surfactant: Prevents the alveoli from “sticking shut” as air moves in

and out Humidifies (keeps alveoli from drying out) Surfactant is the last thing to develop at the end of

gestation

Respiratory membrane: alveoli + capillary Gases diffuse across these thin epithelial layers:

air blood


Lower Respiratory System: Lungs Two lungs: left and right

Right lung has 3 lobes Left lung has 2 lobes and cardiac notch

Function Air distribution to the alveoli Gas exchange between the air and blood


Lung Lobes


Lobule of the Lung


Respiration Step: 1. Pulmonary Ventilation Air flows: atmosphere lungs due to

difference in pressure related to lung volume Lung volume changes due to respiratory muscles

Inhalation (AKA inspiration): diaphragm + external intercostals Diaphragm contracts (moves downward) lung

volume Cohesion between parietal-visceral pleura

lung volume as thorax volume .


Exhalation Exhalation (expiration) is normally passive

process due to muscle relaxation Diaphragm relaxes and rises lung volume External intercostals relax lung volume

Active exhalation: exhale forcefully Example: playing wind instrument Uses additional muscles: internal intercostals,

abdominal muscles


Muscles of Inhalation and Exhalation


Volume-Pressure Changes in Lungs Volume and pressure are inversely related

As lung volume alveolar pressure As lung volume alveolar pressure

Contraction of diaphragm lowers diaphragm lung volume alveolar pressure so it is < atmospheric pressure air enters lungs = inhalation

Relaxation of diaphragm raises diaphragm lung volume alveolar pressure so it is > atmospheric pressure air leaves lungs = exhalation


Volume-Pressure Changes in Lungs


Air Flow Terms Frequency = breaths/min; normal: 12 Tidal volume (TV) = volume moved in one

breath. Normal ~ 500 ml About 70% of TV reaches alveoli (350 ml) Only this amount is involved in gas exchange 30% in airways = anatomic dead space

Minute ventilation (MV) = f x TV = 6000 mL/min


Lung Volumes Measured by spirometer

Inspiratory reserve volume (ERV) = volume of air that can be inhaled beyond tidal volume (TV)

Expiratory reserve volume (IRV) = volume of air that can be exhaled beyond TV

Air remaining in lungs after a maximum expiration = residual volume (RV)


Lung Capacities Inspiratory capacity = TV + IRV Functional residual capacity (FRC) =

RV + ERV Vital capacity (VC) = IRV + TV + ERV (typical

is 4L at rest) Total lung capacity (TLC) = VC + RV


Lung Capacities


Types of Breathing Eupnea - normal breathing Hypernea - increased breathing that is

regulated to meet an increased demand for the body for oxygen (ex: during exercise)

Dyspnea – difficulty breathing Apnea – temporary cessation of breathing

(happens during sleep in some people) Respiratory arrest – failure to resume

breathing following a period of apnea


Reflexes Cough – stimulated by foreign matter in the

trachea or bronchi. The epiglottis closes which increases the air pressure in the lungs. This pressure explodes (cough) which opens the epiglottis suddenly forcing the foreign matter upwards.

Sneeze – stimulated by foreign matter in the nasal cavity. Burst of air is forced through the nose which forces the contaminant out.


Reflexes

Hiccup – spasmodic contraction of the diaphragm usually at the beginning of the inspiration. Soreness results because the diaphragm is a muscle and when it contracts for a length of time it causes soreness. Certain nerve and brain disorders can cause chronic hiccups.

Yawn – slow, deep inspiration. There are many theories, but no confirmed reason for yawning.


Control of Respiration


Other Regulatory Factors of Respiration Respiration can be stimulated by

Limbic system: anticipation of activity, emotion Proprioception as activity is started Increase of body temperature

Sudden pain can apnea: stop breathing Prolonged somatic pain can increase rate

Inflation reflex Bronchi wall stretch receptors inhibit inspiration Prevents overinflation


Aging and the Respiratory System Lungs lose elasticity/ability to recoil more

rigid; leads to Decrease in vital capacity Decreased blood PO2 level Decreased exercise capacity

Decreased macrophage activity and ciliary action Increased susceptibility to pneumonia, bronchitis

and other disorders


Heimlich Maneuver

Do not perform if person can talk or cough. Universal sign of choking is hands to neck. Placing arms around the person, make a fist

with one hand and place it just below the xyphoid process of the sternum, clasp the other hand on top of the fist and push hands in an upward motion toward the heart. This forces the thoracic cavity to shrink and the lungs to force air out, removing the object.


Respiratory Acidosis

Condition that occurs when breathing slows down, which in turn causes CO2 of the blood to then be dissolved as carbonic acid, which in turn raises the acidity of the blood. This causes the heart to speed up, eventually causing a heart attack.

This was the final stage of Christ on the cross following hypovolemic shock.

Copyright 2010, John Wiley & Sons, Inc. Chapter 18 The Respiratory System.

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Transcript of Copyright 2010, John Wiley & Sons, Inc. Chapter 18 The Respiratory System.